CN107936547B - Nylon/graphene/carbon fiber composite powder, preparation method thereof and application thereof in selective laser sintering technology - Google Patents
Nylon/graphene/carbon fiber composite powder, preparation method thereof and application thereof in selective laser sintering technology Download PDFInfo
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Abstract
The invention discloses nylon/graphene/carbon fiber composite powder, a preparation method thereof and application of the nylon/graphene/carbon fiber composite powder in a selective laser sintering technology. The invention provides a preparation method of nylon/graphene/carbon fiber composite powder, wherein the nylon/graphene/carbon fiber composite powder prepared by the method is used as a raw material, and a laser sintering piece obtained by a selective laser sintering technology has good electric conductivity and thermal conductivity and excellent mechanical properties.
Description
Technical Field
The invention relates to the field of selective laser sintering, in particular to nylon/graphene/carbon fiber composite powder, a preparation method thereof and application thereof in a selective laser sintering technology.
Background
Selective Laser Sintering (SLS), also known as selective laser sintering, appeared in the last 80 th century, is a 3D printing technique based on additive manufacturing. The principle of the method is that a layer of powder material (metal powder or nonmetal powder) is paved on a workbench in advance, laser is used for sintering the powder of the solid part under the control of a computer according to interface profile information, and then the powder is circulated continuously and piled layer by layer for forming. The technical requirement is that the powder material has uniform particle size distribution and good fluidity, thus being beneficial to powder bed powder laying. The forming method has the characteristics of simple manufacturing process, high flexibility, wide material selection range, high material utilization rate, high forming speed and the like, is mainly applied to the casting industry aiming at the characteristics of the SLS method, and can be used for directly manufacturing a quick die and the like.
In addition, the SLS process has the greatest advantage of being widely selected, and nylon, wax, ABS, resin-coated sand (precoated sand), polycarbonate (polycarbonate), metal and ceramic powder, etc. can be sintered objects. The unsintered part of the powder bed becomes the support structure for the sintered part and thus the support system (hardware and software) need not be considered.
The nylon material is a semi-crystalline polymer, has good sintering performance and lower melt viscosity, can directly form functional parts with higher density and better mechanical property by an SLS process, and becomes one of SLS forming materials which are most widely applied at present. However, the strength and rigidity of the product formed by the SLS technology are low, and the product cannot meet the mechanical property test requirements of certain formed parts or the property requirements directly used as a final product.
At present, various methods for enhancing the mechanical property of SLS printed parts have appeared, for example, glass fibers and mineral fibers are used for enhancing nylon materials, but the problems of the mechanical property and the surface morphology of the glass fibers and the mineral fibers cause that the enhancement effect is not particularly ideal, and the application requirements of some SLS formed parts cannot be well met. The carbon fiber has the characteristics of light weight, high strength, wear resistance and the like, and the SLS formed piece of the carbon fiber reinforced resin material is greatly improved in strength and modulus compared with the SLS formed piece of the matrix resin material. For example, chinese patent publication No. CN 103951971 a discloses a carbon fiber reinforced resin powder material for selective laser sintering, which includes resin powder, carbon fibers, an antioxidant, a flow aid and a dispersant. And further defines that the resin powder may be nylon or polypropylene. The formed part obtained by the SLS process of the carbon fiber reinforced resin powder material has higher strength and modulus, but the electric and thermal conductivity is poor, so that the application of the formed part obtained by the SLS process in the aspects of electric and thermal conductivity is limited.
Disclosure of Invention
The invention provides a preparation method of nylon/graphene/carbon fiber composite powder, wherein the nylon/graphene/carbon fiber composite powder prepared by the method is used as a raw material, and a laser sintering piece obtained by a selective laser sintering technology has good electric conductivity and thermal conductivity and excellent mechanical properties.
The specific technical scheme is as follows:
a preparation method of nylon/graphene/carbon fiber composite powder comprises the following steps:
(1) mixing graphene, a surfactant and an organic solvent A to obtain a modified graphene dispersion liquid;
(2) mixing nylon, an optionally added anti-sticking agent and an organic solvent B to obtain a mixed solution;
(3) mixing the mixed solution, the modified graphene dispersion solution and a silane coupling agent, placing the mixture in a high-pressure reaction kettle, heating for reaction, decompressing, cooling to room temperature, and performing post-treatment to obtain nylon/graphene composite powder;
(4) and (4) uniformly stirring the nylon/graphene composite powder prepared in the step (3), carbon fibers, a flow aid and an antioxidant to obtain the nylon/graphene/carbon fiber composite powder.
In the step (1):
preferably, the graphene is in a powder shape, has a sheet diameter of less than 100 μm, and is selected from at least one of pure graphene, graphene oxide, reduced graphene oxide and organic modified graphene.
The organic modified graphene comprises organic functionalized graphene obtained by silanization, amidation and adsorption of small molecules and polymers containing aromatic structures on the surface.
More preferably, the sheet diameter of the graphene powder is 10-80 μm.
The organic solvent A is at least one selected from ethanol, ethylene glycol, N-propanol, isopropanol, N-butanol, acetonitrile, formic acid and N, N-dimethylformamide.
The surfactant can be ionic surfactant or nonionic surfactant, such as cationic surfactant such as cetyl amidopropyl trimethyl ammonium chloride, amino acid type zwitterionic surfactant, fatty acid glyceride type nonionic surfactant, etc.
Preferably, the mass ratio of the graphene to the surfactant is 1: 0.1-1; further preferably 1: 1.
Preferably, the mass percentage concentration of graphene in the modified graphene dispersion liquid is 10-50%; more preferably 15 to 25%.
In the step (2):
the nylon of the invention has no special requirements, and common nylon varieties such as nylon 6, nylon 66, nylon 11, nylon 12 and the like can be selected.
Preferably, the anti-sticking agent is selected from at least one of oleamide, erucamide, ethanol bisstearamide and ethanol bislauramide;
the organic solvent B is at least one selected from ethanol, ethylene glycol, N-propanol, isopropanol, N-butanol, acetonitrile, formic acid and N, N-dimethylformamide;
the mass of the anti-sticking agent is 0.1-1% of that of nylon;
the mass percentage concentration of nylon in the mixed solution is 1-25%.
In the step (3):
preferably, the silane coupling agent is at least one selected from aminosilane, vinyl silane and methacryloxy silane; further preferred is vinyltriethoxysilane.
Preferably, the mass of the silane coupling agent is 0.005% to 0.5% of the mass of the nylon in the step (2).
Preferably, the mass ratio of the graphene in the modified graphene dispersion liquid to the nylon in the mixed liquid is 1: 20-1000.
In the invention, the nylon is dissolved in a high-pressure reaction kettle, and the temperature and time of the dissolving process are adaptively adjusted according to the specific nylon type. The silane coupling agent is added to modify the graphene, so that the graphene can be well combined with nylon particles through functional groups, and a good reinforcing effect is achieved.
Preferably, in the step (3), the heating reaction is carried out at the temperature of 130-200 ℃ for 0.5-2 h; the more preferable temperature is 140 to 150 ℃.
Preferably, the cooling rate is 2-5 ℃/min; in order to make the particle size distribution more uniform, the temperature decrease rate is more preferably 4 ℃/min.
The post-treatment comprises drying and sieving, and removing agglomerated large particles by sieving.
In the step (4):
preferably, the diameter of the carbon fiber is 5-20 μm, and the length of the carbon fiber is 10-100 μm;
the flow auxiliary agent is selected from at least one of fumed silica, fumed alumina, nano titanium oxide and nano silicon carbide;
the antioxidant is one or more of hindered phenol antioxidant, phosphite antioxidant, amine antioxidant and sulfo antioxidant, such as antioxidant 168 (tris [2, 4-di-tert-butylphenyl ] phosphite), antioxidant 1098(N, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine), antioxidant 264(2, 6-di-tert-butyl-p-cresol) antioxidant CA (1,1,3 tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane), antioxidant 1076(β - (3, 5-di-tert-butyl-4-hydroxyphenyl) octadecyl propionate), and antioxidant 1010 (tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxy) phenylpropionic acid ] pentaerythritol ester).
The mass fractions of the nylon/graphene composite powder, the carbon fiber, the flow aid and the antioxidant are respectively 70-95%, 0.5-25%, 0.5-4% and 0.1-1%.
Preferably, in the step (4), the nylon/graphene/carbon fiber composite powder prepared in the step (3), the flow aid and the antioxidant are premixed, then the carbon fiber is added, and the mixture is stirred at a high speed of 500-1000 r/min for 10-60 min to obtain the nylon/graphene/carbon fiber composite powder.
Still further preferably, in the nylon/graphene/carbon fiber composite powder, the mass ratio of the carbon fibers to the graphene is 1-7: 1, and the total mass of the carbon fibers and the graphene accounts for 3-12.5% of the total mass of the raw materials.
The invention also discloses the nylon/graphene/carbon fiber composite powder prepared by the method.
The invention also discloses a selective laser sintering technology, which adopts the nylon/graphene/carbon fiber composite powder as raw material powder, and specifically comprises the following steps:
the method comprises the steps of loading raw material powder into a powder supply bin of a selective laser forming machine, uniformly laying the raw material powder on a processing platform by a powder laying scraper, heating to a processing temperature, enabling a laser to emit laser, controlling the laser to scan on the processing platform according to a two-dimensional slice layer by a control program, moving down the thickness of one powder layer after the laser beam scanning is finished, laying the powder by the scraper, scanning the laser beam, and repeating to obtain the laser sintering part.
Preferably, the laser beam is scanned from inside to outside, the laser power is 20-70 w, the scanning speed is 6m/s, the thickness of the powder layer is 0.08-0.15 mm, and the processing temperature is 165-180 ℃.
More preferably, the thickness of the powder layer is 0.12-0.15 mm.
More preferably, the processing temperature is 175 ℃.
Tests show that the nylon/graphene/carbon fiber composite powder prepared by the specific process is used as a raw material, under the action of laser in the selective laser sintering process, the nylon absorbs energy to generate fusion, the graphene is uniformly distributed in the nylon powder, the fused nylon wraps the flaky graphene particles to form an intercalation structure, and meanwhile, the carbon fiber and the graphene are connected to form a network structure, so that the electric conduction and heat conduction performance of a laser sintering piece is improved, and the mechanical performance of the sintering piece is also greatly improved. In the nylon/graphene/carbon fiber composite powder for the selective laser sintering manufacturing technology, graphene is used as a high-strength material, and meanwhile, the nylon/graphene/carbon fiber composite powder has the characteristics of light weight, good flexibility and the like, and carbon fibers have the characteristics of light weight, high strength, wear resistance and the like and have an obvious reinforcing effect. The nylon/graphene/carbon fiber composite material is directly processed by a 3D printing technology, so that the nylon/graphene/carbon fiber composite material has great advantages in the aspects of light weight of parts (automobiles and aerospace), flexibility (flexible electronic devices), high-strength parts and the like compared with the traditional processing technology, and has excellent electric and thermal conductivity.
Compared with the prior art, the invention has the following advantages:
in the preparation process of the nylon/graphene/carbon fiber composite powder disclosed by the invention, the graphene micro-sheets with larger sheet diameter and thickness are used as raw materials, so that the cost is lower. The addition of the anti-sticking agent can avoid the agglomeration of small nylon particles. And the coupling agent is added to ensure that the graphene and the nylon can be well dispersed and mixed. When the nylon/graphene composite powder is prepared, the steps of pressurizing, heating, decompressing and cooling are adopted to enable the particle size distribution of nylon to be more uniform, and the nylon/graphene composite powder is suitable for SLS printing. After the powder is stirred by the high-speed stirrer, the powder is uniformly mixed, and agglomerated large particles are sieved to remove, so that the influence on a subsequent powder bed is avoided, and the graphene and carbon fibers are uniformly distributed in nylon in the sintering process to form a graphene/carbon fiber network structure.
The selective laser sintering process disclosed by the invention is low in laser power and low in energy consumption, the nylon/graphene/carbon fiber composite powder prepared by the process is used as a raw material, graphene and carbon fiber are added into the raw material, and a graphene/carbon fiber network is formed in a laser sintering piece after laser sintering, so that the prepared laser sintering piece has good electric and thermal conductivity, and meanwhile, the mechanical property is greatly improved.
Drawings
Fig. 1 is an SEM image of the nylon/graphene/carbon fiber composite powder prepared in example 1;
FIG. 2 is a graph comparing the thermal conductivity of the laser sintered articles prepared in example 1 with those prepared in comparative examples 1 and 2, respectively;
FIG. 3 is a graph comparing the electrical conductivity of laser sintered parts prepared in example 1 and comparative examples 1 and 2, respectively;
FIG. 4 is a graph comparing tensile properties of laser sintered parts prepared in example 1 and comparative examples 1 and 2, respectively.
Detailed Description
To further clarify the objects, technical solutions and advantages of the present invention, the following detailed description of the present invention is provided with reference to specific examples, which should not be construed as limiting the scope of the present invention.
Example 1
(1) Firstly, screening graphene powder with the particle size of 10-80 mu m by a screening machine.
(2) 870g of nylon 12 powder, 15g of graphene powder, 100g of carbon fiber powder, 10g of fumed silica and 5g of antioxidant 168 were weighed.
(3) Adding graphene and ammonium cetylamide propyl trimethyl chloride into 100g of n-propanol in a mass ratio of 1:1, and performing ultrasonic oscillation for 2-4h to obtain a modified graphene dispersion liquid;
(4) adding 870g of nylon into 4500g of mixed solution of ethanol and ethanol bis-stearamide (the mass of the ethanol bis-stearamide is 0.1% of the mass of the nylon), placing the mixture in a high-pressure reaction kettle, uniformly mixing the mixture with the modified graphene dispersion liquid obtained in the step (3), adding 0.05g of vinyl triethoxysilane, introducing nitrogen, pressurizing to 1MPa, and stirring at a high speed (630 rpm). The temperature is raised to 145 ℃ and the temperature is kept for 1h until the nylon 12 is completely dissolved. After complete dissolution, the high pressure is released, and the temperature is reduced to room temperature at the speed of 4 ℃/min to obtain nylon microparticle suspension;
(5) carrying out vacuum drying treatment on the nylon microparticles prepared in the step (4), and then sieving with a 200-mesh sieve to obtain a nylon/graphene composite powder material;
(6) and (2) placing the prepared nylon/graphene composite powder, fumed silica and an antioxidant 168 in a closed container, uniformly mixing, then adding the weighed carbon fiber powder, and stirring for 20min at the rotating speed of 630 revolutions to obtain the nylon/graphene/carbon fiber (the mass fraction of the carbon fiber is 10%, and the mass fraction of the graphene is 1.5%) composite powder.
(7) Adding nylon/graphene/carbon fiber composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/graphene/carbon fiber composite powder on a processing platform by a powder spreading scraper, emitting laser by a laser, firstly spreading the powder for 6mm, setting the processing temperature to be 175 ℃, setting the processing platform temperature to be 130 ℃, and pre-baking the powder for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
Comparative example 1
A nylon/graphene composite material having a graphene mass fraction of 1.5% was prepared in the proportions described in example 1.
(1) Firstly, screening graphene powder with the particle size of 10-80 mu m by a screening machine.
(2) 985g of nylon 12 powder and 15g of graphene powder were weighed.
(3) Adding graphene and ammonium cetylamide propyl trimethyl chloride into 100g of n-propanol in a mass ratio of 1:1, and performing ultrasonic oscillation for 2-4h to obtain a modified graphene dispersion liquid;
(4) adding 4500g of mixed solution of ethanol and ethanol bis-stearamide (the mass of the ethanol bis-stearamide is 0.1% of the mass of the nylon) into 985g of nylon, placing the nylon in a high-pressure reaction kettle, uniformly mixing the nylon with the modified graphene dispersion liquid obtained in the step (3), adding 0.05g of vinyl triethoxysilane, introducing nitrogen, pressurizing to 1MPa, and stirring at a high speed (630 rpm). The temperature is raised to 145 ℃ and the temperature is kept for 1h until the nylon 12 is completely dissolved. After complete dissolution, the high pressure is released, and the temperature is reduced to room temperature at the speed of 4 ℃/min to obtain nylon microparticle suspension;
(5) carrying out vacuum drying treatment on the nylon microparticles prepared in the step (4), and then sieving with a 200-mesh sieve to obtain a nylon/graphene composite powder material;
(6) adding the nylon/graphene composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/graphene composite powder on a processing platform by a powder spreading scraper, wherein laser is emitted by a laser, powder is firstly spread for 6mm, then the processing temperature is set to be 173 ℃, the processing platform temperature is set to be 130 ℃, and the powder is pre-baked for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
Comparative example 2
A nylon/carbon fiber composite having a carbon fiber mass fraction of 10% was prepared in the proportions described in example 1.
(1) 885g of nylon 12 powder, 100g of carbon fiber powder, 10g of fumed silica and 5g of antioxidant 168 were weighed.
(2) And putting the weighed nylon powder, fumed silica and the antioxidant 168 into a closed container, uniformly mixing, then adding the weighed carbon fiber powder, and stirring for 20min at the rotating speed of 630 revolutions to obtain the nylon/carbon fiber composite powder with the carbon fiber mass fraction of 10%.
(3) Adding nylon/carbon fiber composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/carbon fiber composite powder on a processing platform by a powder spreading scraper, emitting laser by a laser, firstly spreading the powder for 6mm, then setting the processing temperature to be 176 ℃ and the processing platform temperature to be 130 ℃, and pre-baking the powder for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
And (3) performance characterization:
1. heat conductivity
And (3) analyzing and characterizing the thermal conductivity of the prepared laser sintering part by a hot wire method. The results of 3 tests were finally averaged for each laser sintered part. The thermal conductivity of the laser sintered parts prepared in example 1 (designated as PA12/GNPs/C) and comparative examples 1 (designated as PA12/GNPs) and 2 (designated as PA12/C), respectively, are shown in FIG. 2, and pure nylon 12 (designated as PA12) is shown for comparison. As can be seen from FIG. 2, the heat conductivity of the sintered piece of pure nylon 12 is 0.28W/m.K, the heat conductivity of the sintered piece of nylon/graphene composite powder is 0.51W/m.K, the heat conductivity of the sintered piece of nylon/carbon fiber composite powder is 0.78W/m.K, and the increase of the heat conductivity of the sintered piece of nylon/graphene/carbon fiber composite powder is 3.67W/m.K, which is increased by 12 times, which indicates that the graphene and carbon fiber form a network structure inside the sintered piece, and the heat conductivity channels are increased, so that the heat conductivity of the sintered piece is greatly increased.
2. Electric conductivity
The resistivity of the laser sintering part is tested by a high resistance meter, the test result is the average value of three tests, the conductivity of each laser sintering part is shown in figure 3 through formula conversion, and the conductivity data of the pure nylon 12 are given for comparison. As can be seen from the figure, the conductivity of the pure nylon 12 is very low, and stone is addedThe conductivity of the sintered part is from 10 after graphene and carbon fiber- 14S/m is respectively increased to 10-7S/m、10-4S/m order of magnitude, but after the graphene and the carbon fibers are added at the same time, the graphene and the carbon fibers form a network structure in the sintered part, and the conductivity is improved to 10 again-2S/m order of magnitude, and greatly increased conductivity.
3. Mechanical properties
The tensile properties of the laser sintered parts prepared separately from example 1 and comparative examples 1, 2 are given in fig. 4, and the tensile properties of pure nylon 12 are given for comparison. As can be seen from the observation of the graph in FIG. 4, the tensile strength of the pure nylon 12 is 42MPa, the tensile strength of the nylon is basically maintained after the graphene is added, the carbon fiber has a reinforcing effect on the nylon after the carbon fiber is added, and the tensile property of a sintered part is greatly increased. And meanwhile, the graphene and the carbon fibers are added, and the reinforcing effect of the network structure is greater than that of the single fibers, so that the tensile property is further improved to 63 Mpa.
Example 2
(1) Firstly, screening graphene powder with the particle size of 10-80 mu m by a screening machine.
(2) 955g of nylon 12 powder, 15g of graphene powder, 15g of carbon fiber powder, 10g of fumed silica and 5g of antioxidant 168 were weighed.
(3) Adding graphene and ammonium cetylamide propyl trimethyl chloride into 100g of n-propanol in a mass ratio of 1:1, and performing ultrasonic oscillation for 2-4h to obtain a modified graphene dispersion liquid;
(4) adding 955g of nylon into 4500g of mixed solution of ethanol and ethanol bis-stearamide (the mass of the ethanol bis-stearamide is 0.1% of the mass of the nylon), placing the mixed solution in a high-pressure reaction kettle, uniformly mixing the mixed solution with the modified graphene dispersion liquid obtained in the step (3), adding 0.05g of vinyl triethoxysilane, introducing nitrogen, pressurizing to 1MPa, and stirring at a high speed (630 rpm). The temperature is raised to 145 ℃ and the temperature is kept for 1h until the nylon 12 is completely dissolved. After complete dissolution, the high pressure is released, and the temperature is reduced to room temperature at the speed of 4 ℃/min to obtain nylon microparticle suspension;
(5) carrying out vacuum drying treatment on the nylon microparticles prepared in the step (4), and then sieving with a 200-mesh sieve to obtain a nylon/graphene composite powder material;
(6) and (2) placing the prepared nylon/graphene composite powder, fumed silica and an antioxidant 168 into a closed container, uniformly mixing, then adding the weighed carbon fiber powder, and stirring for 20min at the rotating speed of 630 revolutions to obtain the nylon/graphene/carbon fiber (the mass fraction of the carbon fiber is 1.5%, and the mass fraction of the graphene is 1.5%) composite powder.
(7) Adding nylon/graphene/carbon fiber composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/graphene/carbon fiber composite powder on a processing platform by a powder spreading scraper, emitting laser by a laser, firstly spreading the powder for 6mm, setting the processing temperature to be 175 ℃, setting the processing platform temperature to be 130 ℃, and pre-baking the powder for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
Example 3
(1) Firstly, screening graphene powder with the particle size of 10-80 mu m by a screening machine.
(2) 860g of nylon 12 powder, 25g of graphene powder, 100g of carbon fiber powder, 10g of fumed silica and 5g of antioxidant 168 were weighed.
(3) Adding graphene and ammonium cetylamide propyl trimethyl chloride into 100g of n-propanol in a mass ratio of 1:1, and performing ultrasonic oscillation for 2-4h to obtain a modified graphene dispersion liquid;
(4) 860g of nylon is added into 4500g of mixed solution of ethanol and ethanol bis-stearamide (the mass of the ethanol bis-stearamide is 0.1 percent of the mass of the nylon), then the mixed solution is placed into a high-pressure reaction kettle and is uniformly mixed with the modified graphene dispersion liquid obtained in the step (3), 0.05g of vinyl triethoxysilane is added, nitrogen is introduced, the pressure is increased to 1MPa, and the mixture is stirred at a high speed (630 rpm). The temperature is raised to 145 ℃ and the temperature is kept for 1h until the nylon 12 is completely dissolved. After complete dissolution, the high pressure is released, and the temperature is reduced to room temperature at the speed of 4 ℃/min to obtain nylon microparticle suspension;
(5) carrying out vacuum drying treatment on the nylon microparticles prepared in the step (4), and then sieving with a 200-mesh sieve to obtain a nylon/graphene composite powder material;
(6) and (2) placing the prepared nylon/graphene composite powder, fumed silica and an antioxidant 168 into a closed container, uniformly mixing, then adding the weighed carbon fiber powder, and stirring for 20min at the rotating speed of 630 revolutions to obtain the nylon/graphene/carbon fiber (the mass fraction of the carbon fiber is 10%, and the mass fraction of the graphene is 2.5%) composite powder.
(7) Adding nylon/graphene/carbon fiber composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/graphene/carbon fiber composite powder on a processing platform by a powder spreading scraper, emitting laser by a laser, firstly spreading the powder for 6mm, setting the processing temperature to be 175 ℃, setting the processing platform temperature to be 130 ℃, and pre-baking the powder for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
Example 4
(1) Firstly, screening graphene powder with the particle size of 10-80 mu m by a screening machine.
(2) 920g of nylon 12 powder, 15g of graphene powder, 50g of carbon fiber powder, 10g of fumed silica and 5g of antioxidant 168 were weighed.
(3) Adding graphene and ammonium cetylamide propyl trimethyl chloride into 100g of n-propanol in a mass ratio of 1:1, and performing ultrasonic oscillation for 2-4h to obtain a modified graphene dispersion liquid;
(4) adding 4500g of mixed solution of ethanol and ethanol bis-stearamide (the mass of the ethanol bis-stearamide is 0.1% of the mass of the nylon) into 920g of nylon, placing the nylon in a high-pressure reaction kettle, uniformly mixing the nylon with the modified graphene dispersion liquid obtained in the step (3), adding 0.05g of vinyl triethoxysilane, introducing nitrogen, pressurizing to 1MPa, and stirring at a high speed (630 rpm). The temperature is raised to 145 ℃ and the temperature is kept for 1h until the nylon 12 is completely dissolved. After complete dissolution, the high pressure is released, and the temperature is reduced to room temperature at the speed of 4 ℃/min to obtain nylon microparticle suspension;
(5) carrying out vacuum drying treatment on the nylon microparticles prepared in the step (4), and then sieving with a 200-mesh sieve to obtain a nylon/graphene composite powder material;
(6) and (2) placing the prepared nylon/graphene composite powder, fumed silica and an antioxidant 168 into a closed container, uniformly mixing, then adding the weighed carbon fiber powder, and stirring for 20min at the rotating speed of 630 revolutions to obtain the nylon/graphene/carbon fiber (the mass fraction of the carbon fiber is 5%, and the mass fraction of the graphene is 1.5%) composite powder.
(7) Adding nylon/graphene/carbon fiber composite powder into a powder supply bin of a selective laser sintering forming machine, uniformly spreading the nylon/graphene/carbon fiber composite powder on a processing platform by a powder spreading scraper, emitting laser by a laser, firstly spreading the powder for 6mm, setting the processing temperature to be 175 ℃, setting the processing platform temperature to be 130 ℃, and pre-baking the powder for 2 hours. Starting processing after powder baking is finished, controlling the switch of a laser and the angle of a scanner by a computer to enable a laser beam to scan on a processing plane according to the shape of a corresponding two-dimensional slice layer, moving a workbench downwards by one layer thickness after the laser beam is swept, spreading powder, scanning the laser beam, and repeating the steps to obtain a laser sintering piece; the scanning mode of the laser beam on the processing platform is from inside to outside, the laser power is 39W, the scanning speed is 4m/s, and the thickness of the powder layer is 0.12 mm.
The above description is only an embodiment of the present invention and should not be construed as limiting the scope of the present invention, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention.
Claims (10)
1. A preparation method of nylon/graphene/carbon fiber composite powder is characterized by comprising the following steps:
(1) mixing graphene, a surfactant and an organic solvent A to obtain a modified graphene dispersion liquid; the organic solvent A is at least one selected from ethanol, ethylene glycol, N-propanol, isopropanol, N-butanol, acetonitrile, formic acid and N, N-dimethylformamide;
(2) mixing nylon, an anti-sticking agent and an organic solvent B to obtain a mixed solution; the organic solvent B is at least one selected from ethanol, ethylene glycol, N-propanol, isopropanol, N-butanol, acetonitrile, formic acid and N, N-dimethylformamide;
(3) mixing the mixed solution, the modified graphene dispersion solution and a silane coupling agent, placing the mixture in a high-pressure reaction kettle, heating for reaction, decompressing, cooling to room temperature, and performing post-treatment to obtain nylon/graphene composite powder;
(4) and (4) uniformly stirring the nylon/graphene composite powder prepared in the step (3), carbon fibers, a flow aid and an antioxidant to obtain the nylon/graphene/carbon fiber composite powder.
2. The method for preparing the nylon/graphene/carbon fiber composite powder according to claim 1, wherein in the step (1), the graphene is in a powder form, has a sheet diameter of less than 100 μm, and is selected from at least one of pure graphene, graphene oxide, reduced graphene oxide and organic modified graphene;
the mass ratio of the graphene to the surfactant is 1: 0.1-1;
the mass percentage concentration of graphene in the modified graphene dispersion liquid is 10-50%.
3. The method for preparing nylon/graphene/carbon fiber composite powder according to claim 1, wherein in the step (2), the anti-sticking agent is at least one selected from the group consisting of oleamide, erucamide, ethanol bisstearamide and ethanol bislauramide;
the mass of the anti-sticking agent is 0.1-1% of that of nylon;
the mass percentage concentration of nylon in the mixed solution is 1-25%.
4. The method for preparing nylon/graphene/carbon fiber composite powder according to claim 1, wherein in the step (3), the silane coupling agent is at least one selected from aminosilanes, vinylsilanes, and methacryloxysilanes;
the mass of the silane coupling agent is 0.005-0.5% of that of the nylon in the step (2);
the mass ratio of graphene in the modified graphene dispersion liquid to nylon in the mixed liquid is 1: 20-1000.
5. The preparation method of the nylon/graphene/carbon fiber composite powder according to claim 1, wherein in the step (3), the temperature of the heating reaction is 130-200 ℃ and the time is 0.5-2 h;
the cooling rate is 2-5 ℃/min;
the post-treatment comprises drying and sieving.
6. The method for preparing nylon/graphene/carbon fiber composite powder according to claim 1, wherein in the step (4):
the diameter of the carbon fiber is 5-20 mu m, and the length of the carbon fiber is 10-100 mu m;
the flow auxiliary agent is selected from at least one of fumed silica, fumed alumina, nano titanium oxide and nano silicon carbide;
in the nylon/graphene/carbon fiber composite powder, the mass fractions of the components are as follows:
70-95% of nylon/graphene composite powder;
0.5-25% of carbon fiber;
0.5-4% of a flow aid;
0.1-1% of antioxidant.
7. A nylon/graphene/carbon fiber composite powder prepared by the method according to any one of claims 1 to 6.
8. A selective laser sintering technology, which is characterized in that,
the method comprises the following steps: loading raw material powder into a powder supply bin of a selective laser forming machine, uniformly spreading the raw material powder on a processing platform by a powder spreading scraper, heating to a processing temperature, emitting laser by a laser, controlling the laser to scan on the processing platform according to a two-dimensional slice layer by a control program, moving down one powder layer thickness after the laser beam scanning is finished, spreading powder by the scraper, scanning the laser beam, and repeating to obtain a laser sintering part; characterized in that the raw material powder is the nylon/graphene/carbon fiber composite powder according to claim 7;
the laser beam scanning mode is from inside to outside, the laser power is 20-70 w, the scanning speed is 4m/s, the thickness of the powder layer is 0.08-0.15 mm, and the processing temperature is 165-180 ℃.
9. The selective laser sintering technique of claim 8 wherein the thickness of the powder layer is 0.12 to 0.15 mm.
10. The selective laser sintering technique of claim 8 wherein the process temperature is 175 ℃.
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| CN109233272A (en) * | 2018-09-27 | 2019-01-18 | 盱眙欧佰特粘土材料有限公司 | Nylon/attapulgite/carbon fiber composite granule and preparation method thereof and the application in Selective Laser Sintering |
| CN109517377B (en) * | 2018-11-09 | 2020-06-30 | 湖南华曙高科技有限责任公司 | Nylon polymer powder material and preparation method thereof |
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| CN111040444A (en) * | 2019-12-31 | 2020-04-21 | 湖南华曙高科技有限责任公司 | Nylon powder for selective laser sintering and preparation method thereof |
| CN111040435A (en) * | 2019-12-31 | 2020-04-21 | 湖南华曙高科技有限责任公司 | Nylon carbon fiber composite powder material and preparation method thereof |
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